The Research Of The TPMS For Automobile Based On Surface Acoustic Wave

Vehicle tires are the most important parts for the steer's system, tire performance has a direct impact on vehicle performance and safety. If maintaining standard pressure, a vehicle can be manipulated while enhance ease characterization, security, comfort and fuel economy. Meanwhile, it is benefit for extending tire life and lowering cost of automobile use. To achieve these, TPMS-- automobile tire pressure monitoring system is the best tool.The current measuring system TPMS, provides energy to the sensors and transmitters mainly by lithium batteries. TPMS transmitter module is installed in the inside of general tire. The inside of tire is a complex environment, tires rotate in high-speed, the tires'air temperature is up to 160°C, and tires'pressure is within 507 to 810 bar in the general atmosphere. Thus, TPMS involves environmental factors, such as centrifugal acceleration, the weight of the tire dynamic balance, high temperature, and battery life and capacity. So these inevitably bring some disadvantages, such as limited battery life, when the temperature decreases, the battery capacity will decrease, too. This makes the reliability not stable enough. In addition, there are other environmental problems caused by chemical substances in the batteries. If module can be achieved through passive (non-battery), these problems will be solved.SAW sensor has such advantage below: The size is small, weight is light immunity to interference is strong, and it has the advantages of wireless passive. It can be used for non-contact measurement to rotating and fast-moving objects. It is very suitable for automobile tires TPMS. Therefore this paper is based on the Surface Acoustic Wave Principle of tire pressure measuring system. Compare with the traditional TPMS, the surface acoustic wave pressure monitoring system presented in this paper can achieve such advantages as high resolution, small volume and simple structure without batteries.This paper is based on surface acoustic wave sensor, do the research on two surface acoustic wave sensor systems: Delay line and resonant surface acoustic wave sensor system .Though comparison, the indicators of resonant power, such as value, the sensitivity and reliability of wireless detection distance are better than the delay line, so resonant is more suitable for long distance wireless sensor and automotive TPMS measuring system. Thus this paper selects resonator as a surface acoustic wave sensor devices, does research on a new tire pressure monitoring system, and solves the problems that are the complicated structure of the existing system, high costs and limited battery life.The hardware and software of tire pressure measurement system was designed. Sensing surface acoustic wave sensors are the important measuring system components of TPMS. This paper focuses on the design of surface acoustic wave pressure sensitivity analysis. Through design, this paper finds an ideal position placing the surface acoustic wave resonator in the piezoelectric quartz membrane and improves the surface acoustic wave sensor's sensitivity of the pressure, thereby increases the overall system performance. Finally, the surface acoustic wave sensor system was simulated and tested. Main contents are as follows:1. Researching on new TPMS systems, this paper designs a transmitter-receiver system. Analyzing the two receivers, this paper selects once frequency mode. A frequency mode means a simple circuit, and high frequency stability. This paper designs the RF transmitter power amplifier, band-pass filtering and RF excitation signal, this system's signal source selects sinusoidal signal as excitation, takes two source mixing ways; the methods of low noise amplifier and receiver signal receiving are studied. In addition, this paper designs the transceiver circuit switching, mixer, a power amplifier and band-pass filter used in the system, these designs meet the requirements of the system.2. Mainframe is controlled by MSP430F, series of 16-bit micro-controller, this achieves the functions of data collection, the excitation signal sending, receiving encouraging signals, dynamic display, unusual alarm, data storage and so on. System software is design, including system working program, signal processing, in adding the transmitter-receiver system.3. Analyzing the theory on pressure sensitivity of surface acoustic wave. Surface Acoustic Wave Devices and the pressure-sensitive are designed. Quartz is selected as the material of pressure-sensitive patch, and the stress-strain of the pressure-sensitive is analyzed, the size of pressure-sensitive is designed.4. Through creating equivalent circuit model of surface acoustic wave resonator and adding selection parameters, sensor simulation experiments table is built, the simulation is done. Through simulating this paper finds an effective way to encourage surface acoustic wave sensors.